# Hertzsprung-Russell Diagram Lab — Instructor Resources

The NAAP Hertzsprung-Russell Diagram Lab pedagogical objectives are aimed helping students understand some of the properties of stars and how they relate to each other.

- Student Guide: PDF version, MS Word version (last updated 11/13/2011)

The Hertzsprung-Russell Diagram Lab is largely self-contained. Students should have some idea of what a spectra is. This module fits well with discussions about stellar parameters and can serve as a good foundation prior to discussion about stellar evolution.

- The main sequence is defined as the location of stars that are burning hydrogen in the center of the core. The main sequence has no formal, official mathematical definition. Using the Hipparcos data, a curve was fit to the data. This is an approximation since the main sequence has finite thickness. It is more a strip than a line.
- The location of supergiants, giants, and white dwarfs also have no official definitions. The region represented by the module is an approximation.
- The conversion between B-V color index, temperature, and spectral type are not
*precisely*one-to-one conversions. Spectral type, for example, does not have the same resolution as B-V color index. Since most of the data was given in spectral type, some binning occurs in the star data.